People suffer from sensory loss, such as, for example, eyesight loss. Such people can often be totally blind or otherwise legally blind. So called retinal implants can provide stimulation to a recipient to evoke a sight percept. In some instances, the retinal implant is meant to partially restore useful vision to people who have lost their vision due to degenerative eye conditions such as retinitis pigmentosa (RP) or macular degeneration.
Typically, there are three types of retinal implants that can be used to restore partial sight: epiretinal Implants (on the retina), subretinal Implants (behind the retina), and suprachoroidal implants (above the vascular choroid). Retinal implants provide the recipient with low resolution images by electrically stimulating surviving retinal cells. Such images may be sufficient for restoring specific visual abilities, such as light perception and object recognition.
Still further, other types of sensory loss entail somatosensory and chemosensory deficiencies. There can thus be somatosensory implants and chemosensory implants that can be used to restore partial sense of touch or partial sense of smell and/or taste.
Another type of sensory loss is hearing loss, which may be due to many different causes, generally of two types: conductive and sensorineural. Sensorineural hearing loss is due to the absence or destruction of the hair cells in the cochlea that transduce sound signals into nerve impulses. Various hearing prostheses are commercially available to provide individuals suffering from sensorineural hearing loss with the ability to perceive sound. One example of a hearing prosthesis is a cochlear implant.
Conductive hearing loss occurs when the normal mechanical pathways that provide sound to hair cells in the cochlea are impeded, for example, by damage to the ossicular chain or the ear canal. Individuals suffering from conductive hearing loss may retain some form of residual hearing because the hair cells in the cochlea may remain undamaged.
Individuals suffering from hearing loss typically receive an acoustic hearing aid. Conventional hearing aids rely on principles of air conduction to transmit acoustic signals to the cochlea. In particular, a hearing aid typically uses an arrangement positioned in the recipient's ear canal or on the outer ear to amplify a sound received by the outer ear of the recipient. This amplified sound reaches the cochlea causing motion of the perilymph and stimulation of the auditory nerve. Cases of conductive hearing loss typically are treated by means of bone conduction hearing aids. In contrast to conventional hearing aids, these devices use a mechanical actuator that is coupled to the skull bone to apply the amplified sound.
In contrast to hearing aids, which rely primarily on the principles of air conduction, certain types of hearing prostheses, commonly referred to as cochlear implants, convert a received sound into electrical stimulation. The electrical stimulation is applied to the cochlea, which results in the perception of the received sound.
Many devices, such as medical devices that interface with a recipient, have structural and/or functional features where there is utilitarian value in adjusting such features for an individual recipient. One type of medical device where there is utilitarian value in making such adjustments is the above-noted cochlear implant. That said, other types of medical devices, such as other types of hearing prostheses, and other types of prosthesis, such as a retinal implant, exist where there is utilitarian value in fitting such to the recipient.